a cost effective replacement for short and medium span · pdf filea cost effective replacement...
TRANSCRIPT
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A Cost Effective Replacement for Short
and Medium Span Bridges
FlexiArch
Abhey Gupta, Project Manager, Macrete Ireland Limited
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Contents
• Company Introduction• Basic Concept• Background• Origin of Concept• Development of „FlexiArch‟
– Experimental validation: Stability, Strength– Analytical validation
• Applications of „FlexiArch‟– Experience to date– Future developments– Lessons Learned
• Concluding remarks
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Company Introduction
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Macrete Ireland Limited
Mission
To be recognised as a major provider
of precast concrete technology,
products, services and solutions and
to serve our customers regionally,
nationally and internationally.
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• Network Rail
• Water Companies
• Highways Agencies
• Sea Defence
• Marine
• Agriculture
Diverse Markets
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MK Dons Stadium
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Great Yarmouth Harbour
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Cycle Path Tunnel, Cumbria
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Preston Flood Relief
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Boscombe Pier Installation
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South Coast Sea Defence
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FlexiArch Concept
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Origin of Concept – “FlexiArch”
• Historic Methods
• EEC directive 85/3 dated 1999
– The introduction of 40T commercial vehicle
• BD 57/01 and BA 57/01; Design for Durability
(UK Highway Agency)
– No steel / High durability
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Historical Method
Traditional masonry arch
bridges are aesthetic, durable
and strong
However they require
centring and extensive
formwork, which is expensive
and time consuming
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FlexiArch – Historically New
FlexiArch is a modular, unreinforced, precast, concrete
arch bridge system, which is based on the same principles
as traditional stone masonry built arch bridges dating from
Roman times – but without the stone mason.
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Precast concrete blocks
Top layer cast over voussoirs
Polymeric reinforcement
Construction bed
Method of Construction
Casting Voussoirs Polymeric ReinforcementPrecast Voussoirs
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1st Prototype - Paragrid Affixed
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Screed with Crack Inducers
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Lifting of Prototype
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Lifting of Prototype
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Lifting of Prototype
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Setting in Place
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• Is there a market?
– Over 90,000 arch bridges in UK
– Many need repair, strengthening or replacement
• Solution may be simple but required:
– 12 years of laboratory research leading to a patent
– 5 years of R&D within Macrete Ireland Limited
– Attention to detail/quality but cost competitive
Development of FlexiArch
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FlexiArch Testing
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• Model tests at QUB– Third scale: 5 x 2, 10 x 2, 15 x 3. ( metres )– Conventional backfill vs Concrete– Loading to ultimate
• Full scale tests at Macrete Ltd– Stability: 5 x 2, 10 x 2, 15 x 3. ( metres )– Strength: 5 x 2, 10 x 2, 15 x 3. Max 74t
(concrete)
• Full scale tests at actual bridge site – (Tievenameena Bridge, NI)
Experimental Validation
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3rd Scale Single FlexiArch Unit
Test at QUB
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Full Scale Single FlexiArch Unit
Test at Macrete
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Instrumentation of Full Scale Single
FlexiArch Unit Test at Macrete
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Full Scale FlexiArch Bridge
Test at Macrete
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Full Scale Cantilever Test to Verify
Paragrid Creep During Lifting
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Real World Test Site
Tievenameena Bridge
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Instrumentation for Load Test
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Load Test at Site
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Analytical Validation
A range of methods utilised including:
• Reynolds / Mexe
• ARCHIE
• RING
• Spreadsheet methods
• Variable depth beam
• Equivalent grillage for Skew
• Non-linear Finite Element Analysis
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Arch unit
Thrust line
Backing
material
Loading
Passive
pressure
Analysis using ‘ARCHIE ’ software
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Stress Distribution Using FEA
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• Arch ring has acceptable strain levels during lifting
• Arch ring is stable under concrete or granular backfill
• The strength of the arch ring is enhanced with backfill in
place
• Good correlation between test results and the design
software‟s output.
Findings
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FlexiArch Case Study
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Case Study - Devon
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The Site
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Foundation
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Arch delivered
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Lift Stage 1
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Lift Stage 2
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Hanging free
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Placed
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Packed
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Continuing
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Spandrels
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Spandrel Walls Placed
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Ready for concrete fill
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Concrete Fill Completed
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Brick Cladding
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Road Finish
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Completed Bridge
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Advantages of FlexiArch
• Flat pack transportation
• Factory controlled production providing high quality finish
to all elements
• All structural elements are unreinforced concrete,
meaning reduced future maintenance costs (projected
120 years design life)
• Reduced number of on site operatives
• Watercourse / track not disturbed during construction
• Modular construction on site reducing construction time
• Can be cladded to suit client‟s requirements
• Cost competitive with RC alternatives
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FlexiArch Projects
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Access Bridge, FP McCann
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Celbridge – Co. Kildare
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Footbridge, Newtonabbey
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Gloucestershire
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Tievenameena Bridge
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Merthyr Tydfil
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Bentely, Yorkshire
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In Production
Shropshire, Sheinton Bridge - 13.7m Span
Longest commercial FlexiArch to date
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Out to Tender
Jacobs - Clough Brook Culvert
62 FlexiArch units
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Preliminary Design
Sligo – N17
Widening MultiSpan Masonry Arch Bridge
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Anticipated FlexiArch Developments
and Lessons Learned
Flexi Arch
Road Widening
Road Widening
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Tunnels
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• Initially 3m to 10m
• Successfully constructed 15m x 3m
• Consider 20m plus achievable if:
– Adequate crane capacity
– Suitable transport
Increase range of spans
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Skew FlexiArch
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Skew Model
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Setting Out Template for Full Scale
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Aligning Vouissoirs
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Initial Shape During Lifting
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Skew FlexiArch
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Trial Assembly
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Trial Assembly
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Spandrel Attached
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Double Radius FlexiArch
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Geometry Development
Double Radius Arches being developed to fit
Network Rail Profiles
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Double Radius FlexiArch
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1.Modification of footing blocks
– No dowel
– Upstand provided in insitu
abutment instead, full height or to
height of footing unit
Recent Technological Advances
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2.Modification of fixing of spandrel wall
– No longer use tie bars
– Stainless steel brackets provided for fixing
Recent Technological Advances
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3. Revised Concrete Infill - Lower strength infill
is being used with good concrete slab on top
Recent Technological Advances
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4. Provision for Stone Cladding
Brick Cladding
Recent Technological Advances
Original Concrete Finish
Rib slots cast-in
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5. Corbels to be colour matched to stone where
desired for aesthetics
Recent Technological Advances
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40 years 80 years 120 years
Time
Cost
Repair
Capital vs Life Cycle vs Whole Life Costs
Concluding Remarks
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• Precise arch geometry without centring
• Assembly of precast bridge units << 1 day
• Minimal disruption to river / track
• Comparable initial capital cost
• Very durable, no corrodible reinforcement
• Minimum total life cycle cost
• „FlexiArch‟ can greatly enhance use of short /
medium span arch bridges
• Ideal for retrofit and strengthening
Concluding Remarks
“The installation process was straightforward,
went to plan, and was quick.”Andrew Broad, General Works Manager, Dean & Dyball Civil Engineering
(Escot Estate FlexiArch Installation – two bridges)
“The FlexiArch was chosen for the Newtownabbey
cycle path project because of its aesthetic
suitability, economic deployment, sustainable
construction and consideration for environmental
issues such as avoidance of disturbance to the
river bed.”Neil Luney, Rural Project Officer, Newtownabbey Borough Council
(National Cycle Path development on rural land – three bridges)
“The FlexiArch system and installation process
completely suited this location for replacement of
an old arch bridge. There are definitely other
locations within the county where this will be
seriously considered as an appropriate solution
for bridge replacement.”Mladen Dragojlovic, Gloucestershire County Council
(County lane river crossing – bridge replacement)
“The procurement, delivery and erection of the
precast units was extremely efficient. Merthyr
Tydfil CBC and the general public have
expressed extreme satisfaction with the
completed structure.”Mark Robinson, Merthyr Tydfil County Borough Council
(River Taff Corridor Improvements – one bridge)
